IFR just 5.4% of the time

On 2/28/2007 1:40:04 PM, "Jim B" wrote:

I agree with Andrew, I'd love to be able to download historic ASOS
observations for any airport. Even for non-computer programers, a few
minutes parsing with a spread sheet program could yield all kinds of
interesting things!

You might be able to get some information from the METAR archive websites.
Here's one that includes all stations within a US state going back to 1998:

http://vortex.plymouth.edu/sa_parse-u.html

Or, by individual airport:

http://www.uswx.com/us/stn/?code=c&n=1440&stn=kdpa

--
Peter

On 2/28/2007 12:08:47 PM, "Jay Honeck" wrote:

However, I no long harbor the notion that an IR is going to help us
fly more, or longer, or more regularly -- at least not until we can
afford something like a Pilatus.

Now that I have several hundred hours since my instrument rating, I would
never trade it in for a VFR-only rating.

As someone who uses my Bonanza to commute weekly to work and to carry Angel
Flight patients at least monthly, I can attest to the power of an instrument
rating, at least when speaking of flying in the Northeast US.

In the end, it all boils down to where you are based, where you fly often,
and if you have a reason to be at your destination. From the weather I have
seen there, I agree that an IFR rating for those based out of an Arizona
airport would be difficult to maintain without a lot of safety
pilot/under-the-hood type flights.

--
Peter

Thanks Peter!
I've used some of the historic weather websites in the past to "predict"
what the weather may be like during a specific week or month that I had
planned on visiting. Of course, this all has to be taken with a grain of
salt or a voluminous amount of additional weather data!

Interesting side note: My last long cross country trip departed Feb 10 KSTE
(Wisconsin) -KEYW (Key West, FL) Depart KEYW Feb 16 - KSTE 19 hours
hobbs, 1 hour actual IFR = 5.26% IFR. However there were IFR days before,
during, and after.
Jim

"Jay Honeck" wrote in message
ps.com...
As I sit on the ground, on a day off, not flying due to (yet more)
ice, I thought I'd share these interesting results with the group...

Pilots are always surprised when I tell them that Mary and I have
traveled the country extensively by light plane for 12 years, all
VFR. While it's true that we have to be flexible, my experience has
been that it is rare, indeed, that we must cancel a flight due to IFR
conditions that we would have flown in our Pathfinder (a Piper
Cherokee 235), even with the rating.

Many people have questioned the validity of our experience, wondering
if we scud-run everywhere, or are simply not telling the truth. Well,
in a strange twist of fate, a friend of mine recently completed a
study of ASOS observations from 2002 - 2004 here in Iowa City. His
primary goal was to determine prevailing wind direction while IFR
conditions existed, but he inadvertently turned up some interesting
data that supports my informal observations.

During that two year period, he looked at ~33,000 recorded hourly
observations at KIOW. Just 1765 of those observations were IFR, or
5.4%.

Now, of course, there were an unknown number of marginal VFR
conditions in the data set, but these results pretty well confirm my
(non-scientific) observation that showed us canceling just a handful
of flights each year due to weather, and a truly tiny set that were
canceled due to "soft IFR" conditions that we would feel safe flying
Atlas in. Most of our IFR weather in Iowa City is due to icing, fog,
or thunderstorms, meaning that we're not about to challenge Mother
Nature in a Piper Spam Can anyway.

What does this mean? A few conclusions:

1. VFR conditions prevail roughly 95% of the time, even here in the
rough-and-tumble Midwest.
big snip
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

If you're a fun flyer, maybe work for yourself, and don't have a hard and
fast schedule you need to follow, being VFR only ain't a bad thing. On the
other hand, if you need to get somewhere on a schedule, and get back on
schedule, VFR only doesn't get it done.

Your stats showed only 5% or thereabouts IFR weather. Fair enough. So, 5% of
the time, you won't be able to get in or out due to IFR conditions. I'd
venture that there is another 5% where marginal VFR exists and you wouldn't
venture too far from home in those conditions. So, now we're at a 10% no-go
rate.

Extrapolate that to a destination location, which would be no-go 10% of the
time, and you're down to an 80% "go" probability, assuming there isn't
something nasty between here and there. If the X/C is of any distance, there
is probably at least a 5% chance that there is weather bad enough that you
wouldn't cross it VFR. So, now we're down to a 75% chance of launching on a
cross country trip.

The return trip a day or three later has the same weather odds, so if you
multiply the 75% chance of a good trip out by a 75% chance of a good trip
back, the odds of meeting a schedule on a round trip X/C are about 56%...

Time of year and where you are based play a large role here. Presumably if
you live in Arizona you don't see much IFR. On the other hand, on the East
side of the Mississippi, the winter can bring days and even weeks of
marginal weather, and the spring and summer bring fronts and convective
activity that isn't to be trifled with.

KB
(A VFR only pilot with a VFR only airplane...)

On Feb 28, 10:54 am, Thomas Borchert
wrote:
Robert,

I've only had to cancel a very small number of trips because the IFR
was not duable (usually ice). However, I've had lots of trips that
would have been canceled VFR but 0.1 hours of IFR made the trip work.

Exactly. Plus, you just don't have to fret weather decisions as much.
All this doesn't mean at all you're flying in clouds for hours or
approaches to the minimums.

Very true. The VFR pilot stresses about his trip before hand more
often. The IFR rating is worth it even if it just means you are more
confident the trip will go as scheduled.

-Robert

Interesting observations and discussion. I am instrument rated but my
other partner is not. We live and fly up and down the East Coast from
the DC area. He has flown several times down to the Bahamas and back
VFR in our Warrior. For such a long trip I have commented on his
"luck" in making it thru several times without getting grounded. But
maybe its some of those VFR - IFR percentages Jay mentions. I've
never tried to run the comparative stats here.

All I know is that a) when I really want to get somewhere because I
have reservations in some hotel or because I'm visiting family on some
holiday, I don't want to take a chance that the stats will work
against me. And b) as others have noted, I am a MUCH better pilot
than I was before I went thru the instrument training.

Despite what the weather stats may say, I am still a firm believer in
the saying "Having a VFR ticket makes flying fun. Having an IFR
ticket makes it practical."

--Jeff

On Wed, 28 Feb 2007 13:57:15 -0500, Peter R. wrote:


You might be able to get some information from the METAR archive websites.
Here's one that includes all stations within a US state going back to
1998:

http://vortex.plymouth.edu/sa_parse-u.html

Can anyone see a way to get a range of reports from this? I suppose I
could write a little script to query this for each observation over a
block of time, but that seems impolite.

Or, by individual airport:

http://www.uswx.com/us/stn/?code=c&n=1440&stn=kdpa

This gives a maximum of a few days (1440 observations), as far as I can
see. Can anyone see a way to get past that?

Thanks...
- Andrew

On Wed, 28 Feb 2007 10:03:14 -0800, Jay Honeck wrote:

This could be fun, and we've enough people here that we could get the
data for a lot of different airports.

Whew! Clearly your idea of "fun" differs from mine, Andrew

Probably. But then, I'm IRed and current laugh.

-- but I'll
see what I can find out...

Thanks...

Andrew

On Wed, 28 Feb 2007 11:26:17 -0800, Robert M. Gary wrote:

Exactly. Plus, you just don't have to fret weather decisions as much.

Depending upon how you mean this, I'm not sure I agree. I look at the
weather just as much as a VFR pilot. I just look at it a little
differently.

In a way, being VFR-only is *less* work. "Nope, I cannot fly in that" is
a quicker decision than for someone that IFRs.

[...]

The IFR rating is worth it even if it just means you are more confident
the trip will go as scheduled.

As long as one doesn't expect it to yield certainty, I agree with this.

I recall a funny realization when I learned to drive. I was excited to be
able to get places far more quickly than I could by bike. But, once I was
driving, I was immediately even more frustrated by the travel time needed
to get from A to B.

I realized that I'd unconsciously expected travel time to drop to zero.

I also remember being stuck under a ridiculous cloud once, pre-IR. It was
just barely illegal to t/o and fly the perhaps mile or less to get clear
of it (and would have been legal has the airport had no approach {8^).
Everywhere around us was clear sky.

Even the cloud was embarrassed.

- Andrew

On 2/28/2007 2:16:48 PM, "Jim B" wrote:

Interesting side note: My last long cross country trip departed Feb 10 KSTE
(Wisconsin) -KEYW (Key West, FL) Depart KEYW Feb 16 - KSTE 19 hours
hobbs, 1 hour actual IFR = 5.26% IFR. However there were IFR days before,
during, and after.

In contrast, my last long IFR flight was the second week of January this
year, from Buffalo, NY, to Miami, FL, for a business meeting on a Thursday
and back again the following Saturday. About 15 hours total time. The first
day I was actual IMC for the entire first leg of 3.5 hours, with an approach
to minimums at my fuel stop in Tennessee (thanks to a nasty storm off to the
east over North Carolina), and 2.5 hours of the second leg.

On the return trip I estimate being in IMC probably 2 hours of the total 7
hours. This works out to IMC about 53% of the total trip.

--
Peter